Many construction machines such as wheel loaders and hydraulic excavators have working hydraulic actuators driven by hydraulic operating fluid from a hydraulic pump driven by an engine. Some construction machines of this type have the following function. A fan for sending cooling air to objects to be cooled, such as a radiator, a hydraulic operating fluid cooler and the like in an engine room is driven for reverse rotation. Reverse airflow generated in doing so removes the dust that adheres to a filter for dust removal and other objects to be cooled during the normal-rotation drive. Thus, the burden of cleaning the engine room is reduced (see patent document 1, etc.).